Tungsten arc lamp



July 20, 1926'. 1,593,381

F. BLAU I TUNGSTEN ARC LAMP Original Filed April 14, 1921" Inventor: Fritz Blzuu,

H is Attorney.

Patented July 20, 19%.

' UNlTED STATES PATENT orries.

FRITZ BLAH, 01" IBEBLIN-CEEBLOTTENBURG, GERMANY, ASSIGNQB, BY 'MESNE As SIGNMENTS, TO GENERAL ELEGTRIC COMPANY, 015 SCHENECTADY, NEW YORK,

A CORPORATION OF NEW 'YGRK.

T'UNGSTEN ARC LAMP.

briginal application filed. April 14, 1921, Serial No. 461,310, and in Germany April 28, 1920. Divided and this application filed September 22, 1924. Serial No. 738,997.

This invention relates to are lamps of the kind in which the voltaic arc is formed between tungsten electrodes in nitrogen, argon, or the like gases or vapours which are practically indifferent to tungsten.

In the known types of those lamps only one cathode is associated with the anode. Although tungsten metal is a very good conductor of heat its thermal conductivity does not suilice to enable an approximately uniform temperature of the anode to be produced by the voltaic are adjacent to it. Hence a part of its surface does not radiate the light in an economical manner.

Experiments have shown that by associating a plurality of cathodes with an anode, the uniformity of heat conduction in the anode increases rapidly so that by using an adequate number of cathodes an anode of greater extension can be brought to uniform incandescence. In such arrangements it is not possible to use a common series resistance for the various cathodes, because if this were done, an arc would not form or be maintained between each cathode and the anode. A separate series resistance has to be used for each cathode. A. part of the series resistances may be common to the cathodes.

The invention ollers special advantages in cases in which anodes are used which are practically flat. and which are of particular importance for the purposes of optical projection, because the radiation of light in directions in which it ,is not required is limited. Very favourable efi'ects are obtained by placing the cathodes at one side of the anode, preferably near its edge, or by distributing them uniformly in theplane of the anode. I

Two constructional forms of the inven tion are illustrated in the drawing:

Fig. 1 being a longitudinal section;

Fig. 2 representing one half of a plan view and one half of a cross section taken on the dash and dot line of Fig. 1;

Figs. 3 and 4 are circuit diagrams showing the manner of inserting the series resistances in the leads to the cathodes.

In accordance with Fig. 1,"five cathodes b are arranged behind or above the flat anode 'a so that altogether there are six leads 0 leading to the six contact pins (1 of the plug.

According to Fig. 3 a series resistance 6 is inserted in each of the current leads of the live cathodes, whilst in Fig. 4 in addition to the single resistances a part of the series-resistance is common to all 0 the five cathodes.

It may be seen therefore that with the new construction and with the new combination of elements, which I have shown and described, I am enabled to operate a tungsten arc lamp and render the anode substantially uniformly luminous, which has not been done heretofore.-

What I claim as new and desire to secure by Letters Patent of the "United States is:

1. In an enclosed arc lamp, a series of small electrodes rouped about an axis within a circumsc-ri ed area, a comparatively large electrode covering the said area and located in proximity of the small electrodes, a terminal for the large electrode and a terminal for the small electrodes, said terminals adapted to be connected with a source of current whereby a series or arcs may be established between the small electrodes and the large electrode for heating the large electrode to incandescence whereby one side of the large electrode other than the are side may be used as alight emitting surface, said large electrode serving as a shield to separate the light emitted by the said surface from the light emitted by said arcs.

2. In an enclosed tungsten arc, a plate tungsten electrode, a plurality of small electrodes adjacent one side of the plate whereby a series of arcs may be established between the small electrodes and the plate for heating the opposite side of the plate to incandescence whereby said opposite side may beused as a light emitting surface, said plate serving also to shield the arc and the small electrodes and confine both to the shadow of the plate with respect to the said opposite side.

3. In an enclosed arc lamp, a series of electrodes grouped about an axis within a circumscribed area, a comparatively large electrode covering the said area and located in proximity of the small electrodes, a terminal for the large electrode and a terminal for the small electrodes, said terminals adapted to be connected with a source of current whereby a series 0f arcs may oe individual co each small electrode inter- 10 eslehlished between the small elecerodes and posed between the corresponding electrode the large elect-rode for heating the large and the terminal for the small electrodes electrode to incandescence whereby one side and also a resistance interposed between the of the large electzzde other than the arc terminal ofvche small electrodes and the side may used as a light emitting sursource of current. 15

:id is ge ele 'rode ser ing shield In Witness whereof, I have hereunto set is fine light from the arcs an; the my hand this 4th day of September, 1924.

n said surface, and resistance FRITZ BLAU. 

